In order to reduce the noise of combustion and exhaust in an internal combustion engine, exhaust gases from the engine are typically passed through a muffler or through a set of mufflers. In automotive vehicles, the muffler is usually interposed between the free end of an exhaust pipe, which receives exhaust gases from the exhaust manifold of the engine, and a tail pipe, through which exhaust gases are expelled from the vehicle. While many types of mufflers exist, most of them reduce noise by directing exhaust gases through a series of restricted passageways and resonance chambers to allow for gradual expansion of exhaust gas pulses to form a substantially homogeneous flow of gas that is then expelled through the tail pipe.
While such muffler systems have proven extremely effective in reducing the noise of internal combustion engines, they nevertheless have long beer plagued with some persistent problems inherent in their respective designs. One such problem has been the relatively large back pressure that can be developed by such mufflers because of their inherent resistance to the free flow of gases therethrough. Such back pressure produces a load against which the engine must work and, as a consequence, can significantly reduce the engine's running efficiency and its usable power output.
Another problem that can be greatly enhanced by modern muffler systems has been a phenomenon known as reversion whereby back pressure created by the muffler system in conjunction with the partial vacuum in an exhaust pipe that exists just after expulsion of an exhaust pulse combine to create a reverse high pressure pulse that migrates rapidly up the exhaust pipe toward the engine. These reversion pulses can further reduce the running efficiency of the engine and can even migrate all the way to the carburetor of the engine causing carburetor metering difficulties as well as other related problems. The result is a further reduction in the efficiency of and thus the available power produced by the engine.
While the magnitude of the reduction in engine efficiency and power due to back pressure and reversion is often acceptable in the common family automobile, it can be devastating to the overall performance of a race car where even small variations in engine efficiency and usable power can make the difference between winning and loosing a race. As a consequence, designers of race cars have in the past eliminated mufflers altogether from race car exhaust systems and have simply directed the exhaust gases through an unrestricted exhaust pipe for expulsion from the car. In this way, back pressure and reversion phenomenon were generally reduced to acceptable levels.
More recently, however, legislation and local regulations requiring race cars to be equipped with muffler systems for reducing the noise of their engines have been implemented in many areas of the country. Such requirements have resulted in some instances from the expansion of urban populations that has placed residential neighborhoods in close proximity to previously isolated race tracks. As a consequence of such regulations and requirements, race car engineers and drivers have been forced to install mufflers on race cars and particularly on stock car racers of the type commonly raced on oval dirt tracks.
While the requirement for mufflers on racing vehicles has for the most part been successful in reducing the noise associated with the tracks, it nevertheless has presented new and sometimes overwhelming problems to designers and drivers of race cars. Specifically, the back pressure and reversion phenomenon created or at least greatly enhanced by the required mufflers has tended to reduce significantly the efficiency and available power of race car engines on which such mufflers have been installed. Further, the problems created by back pressure and reversion are enhanced for race cars as opposed to, for example, the family car, since race car engines typically operate at extremely high RPM levels and thus rapid and high pressure exhaust expulsion rates.
Attempts to address these problems have generally included enhanced muffler design. While such enhanced design has in some instances reduced back pressure, the reduction has generally not been adequate. Furthermore, reversion, which can be an even more critical problem than back pressure, has yet to be satisfactorily addressed at all. It is therefore to the provision of an improved exhaust system that functions to reduce significantly the back pressure and reversion effects in the system and thus improve engine performance that the present invention is primarily directed.